1. Technical Field
The invention disclosed broadly relates to data processing systems and more particularly relates to improvements in recovery from fault detection in data processing systems.
2. Background Art
Data processing systems have historically suffered from both soft errors and hard errors. Soft errors are usually defined as those deviations from the expected output which occur because of electrical noise or other randomly occurring sources which result in nonreproducible fault syndromes. Hard errors are typically associated with electrical components or mechanical component failures producing errors which are reproducible. Many arrangements for fault tolerant data processing systems have been developed in the prior art. Typical examples of fault tolerant systems is the provision of two or more identical data processing elements operating on the same instruction stream and having their outputs compared with one another. When a difference is detected in the outputs of a pair of data processing elements, it can be inferred that either a soft error or a hard error has occurred. Typically in the prior art, the data processors are then restarted and the instruction stream is executed in a stepwise manner until the error is detected again. If there is no error occurring, then the initial error determination was that of a soft error. If the error is repeated in the stepwise manner, then the instruction at which the error occurs can be identified. This prior art approach to the retrial of instructions after the detection of a fault is a lengthy one. The prior art has not found suitably efficient and fast techniques for the retry of instructions after fault detection.